Speciation rates are positively correlated with the rate of plumage color evolution in hummingbirds

Abstract

A fascinating pattern in nature is the uneven distribution of biodiversity among clades, some with low species richness and phenotypic variation in contrast to others with remarkable species richness and phenotypic diversity. In animals, communication signals are crucial for intra-and interspecific interactions and are likely an important factor in speciation. However, evidence for the association between the evolution of such signals and speciation is mixed. In hummingbirds, plumage coloration is an important communication signal, particularly for mate selection. Here, using reflectance data for 237 hummingbird species (∼66% of total diversity), we demonstrate that color evolution rates are associated with speciation rates, and that differences among feather patches are consistent with an interplay between natural and sexual selection. We found that female color evolution rates of multiple plumage elements, including the gorget, were similar to those of males. Although male color evolution in this patch was associated with speciation, female gorget color evolution was not. In other patches, the relationship between speciation and color evolution rates was pervasive between sexes. We anticipate that future studies on animal communication will likely find that evolution of signaling traits of both sexes has played a vital role in generating signal and species diversity.

Evolution of brilliant iridescent feather nanostructures

“…Some patches may contain a structure with solid platelets, or even mixed structures with both hollow and solid platelets ( Gruson et al, 2019 ). It is notable that the only known examples of interpatch variability in melanosome type come from the birds-of-paradise and hummingbirds—groups that are known to have exceptionally high rates of color evolution ( Beltrán et al, 2021 ; Eliason et al, 2020 ; Ligon et al, 2018 ; Parra, 2010 ). One hypothesis to explain this variation could be that modifications in hollowness/platelet shape tune the brightness of some patches ( Figure 6N–O ).…”

The evolution of sexual dichromatism in a large radiation of landfowls: re-examining the female-biased selection in Wallace’s model

“…We measured the RGB (red, green, blue) values for eight patches (nape, crown, forehead, throat, upper breast, lower breast, face, and lore) on each sex of each species with the R package "colorZapper" [29]. We choose these regions because (1) they are very important signaling regions in Phasianidae showing a variety of colouration [22,23], and (2) they are illustrated clearly in the plates that each patch of all species can be accurately measured. For each patch except lore, a polygon was subjectively selected that contained the representative colouration in that area of the bird's plumage (figure 1a).…”

“…in new world orioles [18], new world blackbirds [11], Australian fairy-wrens [9], grackles-and-allies [10] and starlings [12]), showing that the evolutionary gains of dichromatism are prominently due to the losses in female elaboration. The direction and rates of evolution have been examined as important indicators to understand the accumulation of phenotypic diversity and the pattern of evolutionary diversification [14,[19][20][21][22].…”

“…The direction and rates of evolution have been examined as important indicators to understand the accumulation of phenotypic diversity and the pattern of evolutionary diversification [14,19–22]. Analysing the evolutionray pattern of sexual dichromatism in terms of direction and tempo will allow us to better understand the relative contributions of males and females in the evolutionary process of dichromatism.…”

Hummingbird plumage color diversity exceeds the known gamut of all other birds

“…To better estimate the contribution of feather barbule structural colors to the avian plumage gamut, we investigated the plumage color gamut of the hummingbird family (Trochilidae), which is well known for the diversity and complexity of its barbule structural coloration [9][10][11][12][13][14] (Fig. 1).…”